Binary organic spacer-based quasi-two-dimensional perovskites with preferable vertical orientation and efficient charge transport for high-performance planar solar cells

Quasi-two-dimensional (Q-2D) perovskites ((RNH3)(2)MA(n-1)Pb(n)I(3n+1), RNH3 represents the organic spacer (mostly phenethylammonium (PEA) and n-butylammonium (BA)) and MA = methylammonium) have shown great potential for application in solar cells due to their intrinsic stability, where the organic spacer dominantly determines the Q-2D perovskite ambient stability and device performance. Current studies merely concentrate on unary organic spacer Q-2D perovskites, either using BA or PEA. Herein, for the first time, we have successfully designed and fabricated (PEA(1-x)BA(x))(2)MA(3)Pb(4)I(13) binary spacer-based Q-2D perovskite films, and demonstrated that the device using binary organic spacer-based Q-2D perovskite films has substantially better performance than that using either of the unary organic spacer-based Q-2D perovskite films. The (PEA(0.8)BA(0.2))(2)MA(3)Pb(4)I(13) binary spacer device yields a maximum power conversion efficiency of 15.7%, which outperforms the efficiency record (12-14%) for unary spacer (PEA or BA) Q-2D perovskite devices. In particular, a peak open-circuit voltage of 1.21 V is achieved due to a non-radiative recombination loss of approximate to 100 mV, the lowest reported loss value for Q-2D perovskite devices. The high device performance results from binary-spacer-induced intensified film surface quality, preferable vertical orientation of crystals and improved film optoelectronic properties as well as obviously decreased device recombination losses. These findings open up a new avenue for the rational design of Q-2D perovskite materials with polynary organic spacer.