In recent years, the power conversion efficiency of perovskite solar cells has increased to reach over 20%. Finding an effective means of defect passivation is thought to be a promising route for bringing further increases in the power conversion efficiency and the open-circuit voltage (VOC) of perovskite solar cells. Here, we report the use of an organic halide salt phenethylammonium iodide (PEAI) on HC(NH2)2–CH3NH3 mixed perovskite films for surface defect passivation. We find that PEAI can form on the perovskite surface and results in higher-efficiency cells by reducing the defects and suppressing non-radiative recombination. As a result, planar perovskite solar cells with a certificated efficiency of 23.32% (quasi-steady state) are obtained. In addition, a VOC as high as 1.18 V is achieved at the absorption threshold of 1.53 eV, which is 94.4% of the Shockley–Queisser limit VOC (1.25 V). Planar perovskite solar cells that have been passivated using the organic halide salt phenethylammonium iodide are shown to have suppressed non-radiative recombination and operate with a certified power conversion efficiency of 23.3%.

Surface passivation of perovskite film for efficient solar cells

Although organic photovoltaic (OPV) cells have many advantages, their performance still lags far behind that of other photovoltaic platforms. A fundamental reason for their low performance is the low charge mobility of organic materials, leading to a limit on the active-layer thickness and efficient light absorption. In this work, guided by a semi-empirical model analysis and using the tandem cell strategy to overcome such issues, and taking advantage of the high diversity and easily tunable band structure of organic materials, a record and certified 17.29% power conversion efficiency for a two-terminal monolithic solution-processed tandem OPV is achieved.

https://science.sciencemag.org/content/sci/early/2018/08/08/science.aat2612.full.pdf

Organic and solution-processed tandem solar cells with 17.3% efficiency

The efficiencies of perovskite solar cells have gone from single digits to a certified 22.1% in a few years' time. At this stage of their development, the key issues concern how to achieve further improvements in efficiency and long-term stability. We review recent developments in the quest to improve the current state of the art. Because photocurrents are near the theoretical maximum, our focus is on efforts to increase open-circuit voltage by means of improving charge-selective contacts and charge carrier lifetimes in perovskites via processes such as ion tailoring. The challenges associated with long-term perovskite solar cell device stability include the role of testing protocols, ionic movement affecting performance metrics over extended periods of time, and determination of the best ways to counteract degradation mechanisms.

http://science.sciencemag.org/content/sci/358/6364/739.full.pdf

Promises and challenges of perovskite solar cells

Tandem devices combining perovskite and silicon solar cells are promising candidates to achieve power conversion efficiencies above 30% at reasonable costs. State-of-the-art monolithic two-terminal perovskite/silicon tandem devices have so far featured silicon bottom cells that are polished on their front side to be compatible with the perovskite fabrication process. This concession leads to higher potential production costs, higher reflection losses and non-ideal light trapping. To tackle this issue, we developed a top cell deposition process that achieves the conformal growth of multiple compounds with controlled optoelectronic properties directly on the micrometre-sized pyramids of textured monocrystalline silicon. Tandem devices featuring a silicon heterojunction cell and a nanocrystalline silicon recombination junction demonstrate a certified steady-state efficiency of 25.2%. Our optical design yields a current density of 19.5 mA cm−2 thanks to the silicon pyramidal texture and suggests a path for the realization of 30% monolithic perovskite/silicon tandem devices.

/pdf/fully-textured-monolithic-perovskite-silicon-tandem-solar-tenttrocan.pdf

Fully textured monolithic perovskite/silicon tandem solar cells with 25.2% power conversion efficiency.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pip.2909

Solar cell efficiency tables (version 50)

The efficiency of silicon solar cells has a large influence on the cost of most photovoltaics panels. Here, researchers from Kaneka present a silicon heterojunction with interdigitated back contacts reaching an efficiency of 26.3% and provide a detailed loss analysis to guide further developments.

Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26

Exceeding conversion efficiency of 26% by heterojunction interdigitated back contact solar cell with thin film Si technology

We have developed a 6 inch heterojunction interdigitated back contact (HJBC) solar crystalline Si cell by applying our heterojunction technology and thinfilm technology. To form rear junction and front side passivation, we applied our heterojunction technology that allows efficiency of 24.5% with top/rear contact heterojunction solar cell. To secure this high quality passivation during the HJBC solar cell fabrication process, we have developed deposition technology of insulator layer originally used in thinfilm silicon solar cells. Furthermore, new structure has been designed to drastically suppress the rear electrode resistance. By adapting all these technologies, our HJBC solar cell has reached conversion efficiency of 24.91% independently confirmed at AIST (V OC =737 mV, I SC =10.07 A, FF=80.2 %, P MAX =5.95 W) under 1 sun illumination by total area measurement (239.0 cm2).

6 inch High efficiency back contact crystalline Si solar cell applying heterojunction and thinfilm technology

The method for manufacturing a crystalline silicon substrate for a solar cell includes: forming a texture on the surface of a single-crystalline silicon substrate by bringing an alkali solution and the surface of the single-crystalline silicon substrate into contact with each other; bringing an acidic solution and the surface of the single-crystalline silicon substrate into contact with each other to perform an acid treatment thereon; and then by bringing ozone water and the surface of the single-crystalline silicon substrate into contact with each other to perform an ozone treatment thereon. One aspect of embodiment is that the acidic solution used for the acid treatment is hydrochloric acid. Another aspect of embodiment is that the ozone treatment is performed by immersing the single-crystalline silicon substrate into the ozone water bath.

Method for manufacturing crystalline silicon substrate for solar cell, method for manufacturing crystalline silicon solar cell, and method for manufacturing crystalline silicon solar cell module

PROBLEM TO BE SOLVED: To provide: a solar battery cell superior in performance, in which occurrence of damage in a leak path between separated electrode layers and a crystal silicon substrate can be suppressed, and a method for manufacturing the solar battery cell.SOLUTION: A solar battery cell comprises: a crystal silicon substrate; and a semiconductor region. The semiconductor region is located on a first principal face of the crystal silicon substrate, separated into two regions by a separation groove, and electrically insulated. The semiconductor region includes a semiconductor layer and an electrode layer. When a direction from the first principal face toward the semiconductor region is defined as an upward direction, in the solar battery cell where the electrode layer is located at an upper face side of the semiconductor layer, a shortest distance Wt between the electrode layer of one of the semiconductor regions opposed to each other with the separation groove interposed therebetween and the electrode layer of the other semiconductor region is 1.2 times or more and 10 times or less as large as a shortest distance Wn between the semiconductor layer of the one semiconductor region and the semiconductor layer of the other semiconductor partial region.SELECTED DRAWING: Figure 6

Yoshida Wataru

Papers

Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26

Exceeding conversion efficiency of 26% by heterojunction interdigitated back contact solar cell with thin film Si technology

6 inch High efficiency back contact crystalline Si solar cell applying heterojunction and thinfilm technology

Method for manufacturing crystalline silicon substrate for solar cell, method for manufacturing crystalline silicon solar cell, and method for manufacturing crystalline silicon solar cell module

Solar battery cell, and method for manufacturing solar battery cell