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Perovskite solar cells (PSCs) with state-of-the-art efficiencies contain thermally unstable methylammonium (MA). Avoiding MA molecules usually leads to a severe decrease in the cell efficiency. In this work, a novel ion liquid (simplified as NDAPBF4) possessing a pyridine cation and BF4− anion were introduced to improve the performance of MA-free PSCs. The ion liquid NDAPBF4 can optimize the grain growth of the perovskite, leading to reduced carrier traps. In particular, NDAPBF4 served as an n-type dopant and boosted the electron transportation in the perovskite films, which further suppressed the carrier non-radiative recombination at the interface between the perovskite and the electron transporting layer. Finally, PSCs with a Cs0.05FA0.95PbI3 perovskite film as the absorber achieved a remarkable efficiency of 21.25%, which was one of the highest MA-free inverted perovskite solar cells up to date. PSCs doped with NDAPBF4 also gave excellent stability, which preserved 95% and 94% of the initial efficiency after being aged for 1000 h and 500 h under room temperature and elevated temperature at 85 °C, respectively. [ABSTRACT FROM AUTHOR]

A novel zwitterion named bethanechol chloride (BTCC) was introduced to simultaneously stabilize a Pb–I framework and passivate defects for efficient inverted perovskite solar cells. The BTCC-assisted device yielded an elevated power conversion efficiency of 20.45% with an open-circuit voltage of 1.14 V. [ABSTRACT FROM AUTHOR]

Defect-passivation functional groups have been extensively explored in perovskite solar cells (PSCs) in recent years; however, most of these groups were organic, and the integration of inorganic functional groups with organic matrixes bearing other functions has rarely been reported. Here, to demonstrate the effectiveness of this integration, the combination of an inorganic group, K+ ion, and an organic conjugated polyelectrolyte (CPE) matrix which serves as a hole transporting material (HTM) is attempted. The resulting CPE material TB(K) presents much stronger abilities for defect-passivation and hole-extraction, and thus yields a much increased power conversion efficiency (PCE) of 20.01% and increased long-term stability when applied to inverted PSC devices compared with its control polymer TB(Na), where only the inorganic cations are varied from a defect-passivation group to a common one. [ABSTRACT FROM AUTHOR]

Quasi-two-dimensional (Q-2D) perovskites ((RNH3)2MAn−1PbnI3n+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 (PEA1−xBAx)2MA3Pb4I13 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 (PEA0.8BA0.2)2MA3Pb4I13 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 ∼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. [ABSTRACT FROM AUTHOR]

Exploring competent electrocatalysts for the oxygen evolution reaction (OER) is central to the development of a clean, reliable and emission-free hydrogen economy. Perovskites have been seen as promising OER electrocatalysts among all the potential candidates so far. Here, we introduced redox inactive Zr and Y ions to meliorate the redox capability of active ions and prepared BaCo0.5−xFe0.5−xZrxYxO3−δ (BCF(ZY)x, x = 0.0−0.2) oxides as efficient electrocatalysts for the OER. The catalyst of BCF(ZY)0.1 exhibits a higher OER activity (including disk activity, intrinsic activity and mass activity) and better durability than the gold-standard OER electrocatalyst IrO2 and the well-known Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) perovskite. The overpotential to deliver an electrode current density of 10 mA cm−2 of BCF(ZY)0.1 oxide is merely 0.32 V in 1 M KOH, and the intrinsic activity of BCF(ZY)0.1 is ∼52 times higher than IrO2. The outstanding electro-catalytic activity and stability of BCF(ZY)0.1 are attributed to the increased redox ability compared with BSCF, including the faster charge transfer process and much more facile adsorption of OH− and desorption of O2. [ABSTRACT FROM AUTHOR]

A delicate control of crystallization and morphology of perovskite absorbers is critical to obtain high performance hybrid perovskite solar cells (PSCs). Here, we have developed a novel crystallization strategy which involves hydration water induced intermediate phase formation under heat assisted spin-coating processing (HASP) to manipulate the morphology and grain size of perovskite films, and thus it can avoid the use of toxic and volatile antisolvents used in conventional one-step solution processes to make PSCs. During HASP, impressive morphological evolution of films occurs with the formation of CH3NH3PbI3·xH2O perovskite intermediate phases. With ingenious control of the crystallization kinetics, highly crystalline perovskite films with fewer defect states and high carrier lifetimes are obtained. The corresponding PSCs exhibit a power conversion efficiency (PCE) of 19.12% with a stabilized power output efficiency of 18.89% at the maximum power point, which is a 70% enhancement compared to that of conventional one-step process based PSCs. Furthermore, the PSC fabricated by the HASP method achieved a PCE of 15.47% with an active area of 1.2 cm2. Moreover, the flexible PSCs fabricated by the HASP method achieved a record efficiency of 14.87% with negligible hysteresis for PEDOT:PSS-based flexible inverted PSCs. Our work opens up a new avenue for morphology and crystallization control through hydration water induced intermediate phase formation under HASP, which paves the way toward further enhancing the device performance of perovskite solar cells. [ABSTRACT FROM AUTHOR]

A new alternating copolymer of fluorene and naphthalene diimide, PF-NDI, was synthesized and characterized. The highest power conversion efficiency of all-polymer solar cells based on P3HT:PF-NDI reached 1.63% with a relatively high fill factor of 0.66 by using 1,8-diiodooctane as a solvent additive to optimize the mixing morphology., (This journal is © The Royal Society of Chemistry 2012)