Preparation of perovskite with photoelectric conversion efficiency of 27% by Dalian Institute of Chemicals

[ Instrument Network Instrument Development ] Recently, Liu Shengzhong, a researcher of the Thin Film Silicon Solar Cell Research Group (DNL1606) of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and Yang Dong, a researcher at Shaanxi Normal University, adopted a translucent perovskite battery and a high-efficiency silicon heterojunction film. The battery is combined to form a four-terminal perovskite-silicon tandem solar cell with a photoelectric conversion efficiency of 27.0%.

Crystalline silicon solar cells are the first generation of solar cells. After decades of development, the technology is very mature. Currently, 95% of the PV market share is occupied by crystalline silicon solar cells. The photoelectric conversion efficiency of the best crystalline silicon solar cells reported by the laboratory has reached 26.6%, which is very close to its theoretical photoelectric conversion efficiency limit of 29.4%. Under the laws of physics, the efficiency of crystalline silicon cells is becoming narrower and narrower. In order to achieve higher photoelectric conversion efficiency, more and more research has begun to focus on stacking cells with crystalline silicon cells and other high-efficiency batteries.

Perovskite battery is the third generation of solar cell developed in recent years. It has the advantages of abundant raw materials, low cost, simple preparation process and good tolerance to defects. At present, the photoelectric conversion efficiency of the perovskite battery reported by the laboratory has exceeded 24%. The structure of the perovskite is ABX3, and the A site is usually a positive monovalent organic cation CH3NH3+, NH=CHNH3+ or an inorganic Cs+ ion, and the B site is usually a positive divalent metal cation Pb2+, Sn2+ or the like. X is usually a halogen anion I-, Br-, Cl- or the like. By ion replacement, the band gap of perovskites can be flexibly adjusted from 1.4 to 2.3 eV, making it an ideal laminate battery cell material.

The laminated battery consists of a high band gap subcell and a low band gap subcell. Low bandgap sub-cells broaden the utilization of solar photons; high bandgap sub-cells reduce the thermal energy loss of the relaxation process after electronic capture of high-energy photons. Therefore, the laminate battery has a higher ultimate photoelectric conversion efficiency than the single junction battery. One of the keys to obtaining a highly efficient tandem solar cell is to prepare a transparent electrode under mild conditions, that is, to prepare an electrode having high conductivity and high light transmittance without damaging the underlying material.

The team used vacuum thermal evaporation to deposit thin films using a molybdenum trioxide/gold nanoweb/molybdenum trioxide “sandwich structure” as a transparent electrode to replace the metal back electrode in a traditional perovskite battery. The prepared translucent perovskite solar cell has a photoelectric conversion efficiency of 18.3%, which is one of the highest efficiencies of translucent perovskite batteries currently prepared using ultra-thin metals. This translucent perovskite solar cell was combined with a silicon heterojunction thin film battery having a photoelectric conversion efficiency of 23.3% to obtain a four-terminal tandem solar cell having a photoelectric conversion efficiency of 27.0%.

The study used a simple and low-cost method to prepare transparent electrodes with high conductivity and high light transmittance, which helped to promote the development of translucent cells and multi-junction/stack cells, reducing the cost of photovoltaic power generation. Relevant results were published in Advanced Functional Materials. The work was funded by the National Natural Science Foundation of China, China's National Key Research and Development Program, and Shaanxi Science and Technology Innovation Guidance Project.