Despite the exciting progress on power conversion efficiencies, the commercialization of the emerging lead (Pb) halide perovskite solar cell technology still faces significant challenges, one of which is the inclusion of toxic Pb. Searching for Pb-free perovskite solar cell absorbers is currently an attractive research direction. The approaches used for and the consequences of Pb replacement are reviewed herein. Reviews on the theoretical understanding of the electronic, optical, and defect properties of Pb and Pb-free halide perovskites and perovskite derivatives are provided, as well as the experimental results available in the literature. The theoretical understanding explains well why Pb halide perovskites exhibit superior photovoltaic properties, but Pb-free perovskites and perovskite derivatives do not.

From Lead Halide Perovskites to Lead-Free Metal Halide Perovskites and Perovskite Derivatives

Recently, two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted a huge amount of interest due to their unique layered structure, and potential optical properties. However, amongst researchers it has long been disputed as to whether it is suitable for use as a photovoltaic material or light-emitting device. Here, we present a detailed theoretical investigation to discuss the photovoltaic and optoelectronic properties of a novel synthetic 2D layered perovskite (PEA)2PbI4. Based on the calculated geometric and electronic structure, charge carrier mobilities of the 2D layered (PEA)2PbI4 are predicted theoretically. In addition, the linear dichroism and exciton binding energies are also calculated. We found that the carrier mobilities of the 2D layered (PEA)2PbI4 reach the same order of magnitude as those of the optoelectronic material MoS2, but smaller than those of the photovoltaic material MAPbI3 and Si crystal, whereas exciton binding energies (Eb) enlarge with the thinning layers, being obviously higher than MAPbI3 and Si crystal. Moreover, the system exhibits a strong linear dichroism, suggesting weak absorption along the c axis in the visible spectrum, which is detrimental to photovoltaics. Our work provides a theoretical basis to prove that ultrathin two-dimensional (2D) materials may be potential candidates for optoelectronic detection devices, rather than solar absorbers.

Layer-dependent transport and optoelectronic property in two-dimensional perovskite: (PEA)2PbI4

Lead halide perovskites have displayed the highest solar power conversion efficiencies of 23% but the toxicity issues of these materials need to be addressed. Lead-free perovskites have emerged as viable candidates for potential use as light harvesters to ensure clean and green photovoltaic technology. The substitution of lead by Sn, Ge, Bi, Sb, Cu and other potential candidates have reported efficiencies of up to 9%, but there is still a dire need to enhance their efficiencies and stability within the air. A comprehensive review is given on potential substitutes for lead-free perovskites and their characteristic features like energy bandgaps and optical absorption as well as photovoltaic parameters like open-circuit voltage (V OC), fill factor, short-circuit current density (J SC), and the device architecture for their efficient use. Lead-free perovskites do possess a suitable bandgap but have low efficiency. The use of additives has a significant effect on their efficiency and stability. The incorporation of cations like diethylammonium, phenylethyl ammonium, phenylethyl ammonium iodide, etc., or mixed cations at different compositions at the A-site is reported with engineered bandgaps having significant efficiency and stability. Recent work on the advancement of lead-free perovskites is also reviewed.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/gch2.201900050

Potential Substitutes for Replacement of Lead in Perovskite Solar Cells: A Review.

Insight into lead-free organic-inorganic hybrid perovskites for photovoltaics and optoelectronics: A first-principles study

Over the last two decades, advancements in photovoltaic (PV) technology have been flourishing due to the continuous flow of valuable findings. Relevant insights on recent improvements, manufacturing approaches, and various applications of PV technology are provided. Both the PV cell structure and conversion efficiency may significantly contribute to the progression of the PV system. Currently, a wide range of advanced materials and smart technologies are employed within the PV cell's architecture, improving its structure; i.e. PERC/PERL, IBC, HIT/HJT, and MWT. The applications of nanoparticles and thin film technology in PV cell structures have successfully opened new research prospects to boost PV efficiency and overcome certain limitations with the use of CdSe, ZnCds, CdTe, a-Si/µc-Si, CIS, and CIGS. Additionally, constant development in the third generation of OSC methods using OE, OM, and COP are conducted. The improvement of PV backsheet structures and their enhanced optical properties yielded promising results in optimizing solar radiation, reflectance, and PV cell competence. The emergence of hybrid technologies (e.g. PVTE and TPV systems) led to effective solutions for reducing excessive heat that cause deficiency to a PV cell's functionality. Overall, modelling and effectively implementing appropriate parameters (such as diode parameters, optical parameters, circuit current, circuit voltage, fill factor (FF), conversion efficiency, IR, and UV spectral parameters) contributed to the total efficiency and performance modelling of the PV system.

/pdf/photovoltaic-applications-status-and-manufacturing-prospects-5fojcwmita.pdf

Pe-Bing He

Papers

Geometric structure and photovoltaic properties of mixed halide germanium perovskites from theoretical view