Low-temperature solution-processed perovskite solar cells with high efficiency and flexibility

Perovskite compounds have attracted recently great attention in photovoltaic research. The devices are typically fabricated using condensed or mesoporous TiO₂ as the electron transport layer and 2,2′7,7′-tetrakis-(N,N-dip-methoxyphenylamine)9,9′- spirobifluorene as the hole transport layer. However, the high-temperature processing (450 C) requirement of the TiO₂ layer could hinder the widespread adoption of the technology. In this report, we adopted a low-temperature processing technique to attain high-efficiency devices in both rigid and flexible substrates, using device structure substrate/ITO/PEDOT:PSS/ CH₃NH₃PbI_3-xCl_x/PCBM/Al, where PEDOT:PSS and PCBM are used as hole and electron transport layers, respectively. Mixed halide perovskite, CH₃NH₃PbI_3-xCl _x, was used due to its long carrier lifetime and good electrical properties. All of these layers are solution-processed under 120 C. Based on the proposed device structure, power conversion efficiency (PCE) of 11.5% is obtained in rigid substrates (glass/ITO), and a 9.2% PCE is achieved for a polyethylene terephthalate/ITO flexible substrate.