Petr P. Khlyabich

Bio: Petr P. Khlyabich is an academic researcher from Princeton University. The author has contributed to research in topics: Polymer solar cell & Organic solar cell. The author has an hindex of 23, co-authored 42 publications receiving 2943 citations. Previous affiliations of Petr P. Khlyabich include Russian Academy of Sciences & Unitary enterprise.

Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

Abstract: Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

Efficient organic solar cells with helical perylene diimide electron acceptors.

Abstract: We report an efficiency of 6.1% for a solution-processed non-fullerene solar cell using a helical perylene diimide (PDI) dimer as the electron acceptor. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor–acceptor interfaces, indicating that charge carriers are created from photogenerated excitons in both the electron donor and acceptor phases. Light-intensity-dependent current–voltage measurements suggested different recombination rates under short-circuit and open-circuit conditions.

Efficient ternary blend bulk heterojunction solar cells with tunable open-circuit voltage.

Abstract: To explore the potential of ternary blend bulk heterojunction (BHJ) photovoltaics as a general platform for increasing the attainable performance of organic solar cells, a model system based on poly(3-hexylthiophene) (P3HT) as the donor and two soluble fullerene acceptors, phenyl-C61-butyric acid methyl ester (PC61BM) and indene-C60 bisadduct (ICBA), was examined. In all of the solar cells, the overall ratio of polymer to fullerene was maintained at 1:1, while the composition of the fullerene component (PC61BM:ICBA ratio) was varied. Photovoltaic devices showed high short-circuit current densities (Jsc) and fill factors (FF) (>0.57) at all fullerene ratios, while the open-circuit voltage (Voc) was found to vary from 0.61 to 0.84 V as the fraction of ICBA was increased. These results indicate that the Voc in ternary blend BHJ solar cells is not limited to the smallest Voc of the corresponding binary blend solar cells but can be varied between the extreme Voc values without significant effect on the Jsc or ...

Origin of the tunable open-circuit voltage in ternary blend bulk heterojunction organic solar cells.

Abstract: Ternary blend bulk heterojunction organic solar cells comprising either a polythiophene donor and two fullerene acceptors or two polythiophene donors and a fullerene acceptor are shown to have unique electronic properties. Measurements of the photocurrent spectral response and the open-circuit voltage show that the HOMO and LUMO levels change continuously with composition in the respective two-component acceptor or donor pair, consistent with the formation of an organic alloy. However, optical absorption of the exciton states retains the individual molecular properties of the two materials across the blend composition. This difference is attributed to the highly localized molecular nature of the exciton and the more delocalized intermolecular nature of electrons and holes that reflect the average composition of the alloy. As established here, the combination of molecular excitations that can harvest a wide range of photon energies and electronic alloy states that can adjust the open-circuit voltage provides the underlying basis of ternary blends as a platform for highly efficient next-generation organic solar cells.

Compositional Dependence of the Open-Circuit Voltage in Ternary Blend Bulk Heterojunction Solar Cells Based on Two Donor Polymers

Abstract: Ternary blend bulk heterojunction (BHJ) solar cells containing as donor polymers two P3HT analogues, high-band-gap poly(3-hexylthiophene-co-3-(2-ethylhexyl)thiophene) (P3HT75-co-EHT25) and low-band-gap poly(3-hexylthiophene–thiophene–diketopyrrolopyrrole) (P3HTT-DPP-10%), with phenyl-C61-butyric acid methyl ester (PC61BM) as an acceptor were studied. When the ratio of the three components was varied, the open-circuit voltage (Voc) increased as the amount of P3HT75-co-EHT25 increased. The dependence of Voc on the polymer composition for the ternary blend regime was linear when the overall polymer:fullerene ratio was optimized for each polymer:polymer ratio. Also, the short-circuit current densities (Jsc) for the ternary blends were bettter than those of the binary blends because of complementary polymer absorption, as verified using external quantum efficiency measurements. High fill factors (FF) (>0.59) were achieved in all cases and are attributed to high charge-carrier mobilities in the ternary blends. ...

An electron acceptor challenging fullerenes for efficient polymer solar cells.

Abstract: A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized. Fullerene-free polymer solar cells (PSCs) based on the ITIC acceptor are demonstrated to exhibit power conversion effi ciencies of up to 6.8%, a record for fullerene-free PSCs.

Organic solar cells based on non-fullerene acceptors.

Abstract: Organic solar cells (OSCs) have been dominated by donor:acceptor blends based on fullerene acceptors for over two decades. This situation has changed recently, with non-fullerene (NF) OSCs developing very quickly. The power conversion efficiencies of NF OSCs have now reached a value of over 13%, which is higher than the best fullerene-based OSCs. NF acceptors show great tunability in absorption spectra and electron energy levels, providing a wide range of new opportunities. The coexistence of low voltage losses and high current generation indicates that new regimes of device physics and photophysics are reached in these systems. This Review highlights these opportunities made possible by NF acceptors, and also discuss the challenges facing the development of NF OSCs for practical applications.

Non-fullerene acceptors for organic solar cells

Abstract: Non-fullerene acceptors (NFAs) are currently a major focus of research in the development of bulk-heterojunction organic solar cells (OSCs). In contrast to the widely used fullerene acceptors (FAs), the optical properties and electronic energy levels of NFAs can be readily tuned. NFA-based OSCs can also achieve greater thermal stability and photochemical stability, as well as longer device lifetimes, than their FA-based counterparts. Historically, the performance of NFA OSCs has lagged behind that of fullerene devices. However, recent developments have led to a rapid increase in power conversion efficiencies for NFA OSCs, with values now exceeding 13%, demonstrating the viability of using NFAs to replace FAs in next-generation high-performance OSCs. This Review discusses the important work that has led to this remarkable progress, focusing on the two most promising NFA classes to date: rylene diimide-based materials and materials based on fused aromatic cores with strong electron-accepting end groups. The key structure–property relationships, donor–acceptor matching criteria and aspects of device physics are discussed. Finally, we consider the remaining challenges and promising future directions for the NFA OSCs field. Non-fullerene acceptors have been widely used in organic solar cells over the past 3 years. This Review focuses on the two most promising classes of non-fullerene acceptors — rylene diimide-based materials and fused-ring electron acceptors — and discusses structure–property relationships, donor– acceptor matching criteria and device physics, as well as future research directions for the field.

Fullerene-Free Polymer Solar Cells with over 11% Efficiency and Excellent Thermal Stability

Abstract: A nonfullerene-based polymer solar cell (PSC) that significantly outperforms fullerene-based PSCs with respect to the power-conversion efficiency is demonstrated for the first time. An efficiency of >11%, which is among the top values in the PSC field, and excellent thermal stability is obtained using PBDB-T and ITIC as donor and acceptor, respectively.