Engineering the architecture of perovskite photovoltaics

Abstract

Photovoltaic (PV) technology based on organo-metal halide perovskites (OHPs) offers a promising prospect for the next breakthrough in renewable energy generation. Due to the high absorption coefficients, low exciton binding energy, and balanced charge transport properties with long diffusion lengths, the initial efficiency of such technology of around 3% has been rapidly increased to values as high as 22%, comparable to most inorganic thin film PV technologies. In order to become commercially viable, the reproducibility of unit cell efficiency as well as scalable module geometry should be insured. Moreover, distinctive features that cannot be afforded by traditional silicon PV should be developed. Phosphorous impurity in precursor solution of $CH_3NH_3PbI_3$ ($MAPbI_3$) was investigated for its effect on enhancing not only the efficiency (avg. efficiency of 13.5%) but also the reproducibility (standard deviation of 0.47) of perovskite solar cells (psSCs). Joint analysis on the experimental results and the electrical modeling of psSCs indicated that minority carrier lifetime and the doping concentration of perovskite layer are highly related to the performance of perovskite photovoltaic devices. In an effort to develop distinctive functionality in psSCs, semi-transparent PV devices utilizing a metal-based transparent electrode that has a thermal-mirror property were realized. Through intentionally applying a thick metal layer, but still transmissive in the visible wavelength, substantial reflection at the near-infrared (NIR) region was recognized, thereby realizing NIR solar energy rejection of 85.5%. Lastly, a cost-effective module architecture that can be utilized for vacuum-deposited thin film PVs is presented. The present study focuses on developing a scalable module fabrication process that can minimize the efficiency loss originating from the interconnection regions. By applying a combination process consist of printing and oblique deposition, an inactive length of 415$\mu$m was realized.