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Organic semiconducting materials that are optically transparent in the near-ultraviolet (NUV) region from 300 to 400 nm are needed for advanced perovskite devices such as bifacial semitransparent a...

Perovskite solar cells have rapidly been developed over the past several years. Choice of the most suitable solar cell structure is crucial to improve the performance further. Here, we attempt to determine an optimum cell structure for methylammonium lead iodide (MAPbI3) perovskite sandwiched by TiO2 and spiro-OMeTAD layers, among planar heterojunction, mesoporous structure, and extremely thin absorber structure, by identifying and comparing charge carrier diffusion coefficients of the perovskite layer, interfacial charge transfer, and recombination rates using transient emission and absorption spectroscopies. An interfacial electron transfer from MAPbI3 to compact TiO2 occurs with a time constant of 160 ns, slower than the perovskite photoluminescence (PL) lifetime (34 ns). In contrast, fast non-exponential electron injection to mesoporous TiO2 was observed with at least two different electron injection processes over different time scales; one (60–70%) occurs within an instrument response time of 1.2 ns...

Herein, the open-circuit voltage (V[OC]) loss in both polymer solar cells and perovskite solar cells is quantitatively analyzed by measuring the temperature dependence of V[OC] in order to discuss the difference in the primary loss mechanism of V[OC] between them. As a result, the photon energy loss for polymer solar cells is in the range of 0.7–1.4 eV, which is ascribed to temperature-independent and -dependent loss mechanisms while that for perovskite solar cells is as small as about 0.5 eV, which is ascribed to a temperature-dependent loss mechanism. This difference is attributed to the different charge generation and recombination mechanisms between the two devices. The potential strategies for the improvement of V[OC] in both solar cells are further discussed on the basis of the experimental data.

Organic–inorganic hybrid perovskite solar cells are attracting much attention due to their excellent photovoltaic properties. In these multilayered structures, the device performance is determined by complicated carrier dynamics. Here, we studied photocarrier recombination and injection dynamics in CH3NH3PbI3 perovskite solar cells using time-resolved photoluminescence (PL) and photocurrent (PC) measurements. It is found that a peculiar slowdown in the PL decay time constants of the perovskite layer occurs for higher excitation powers, followed by a decrease of the external quantum efficiency for PC. This indicates that a carrier-injection bottleneck exists at the heterojunction interfaces, which limits the photovoltaic performance of the device in concentrator applications. We conclude that the carrier-injection rate is sensitive to the photogenerated carrier density, and the carrier-injection bottleneck strongly enhances recombination losses of photocarriers in the perovskite layer at high excitation co...

Solution-processed organo-lead halide perovskite solar cells with deep pinholes in the perovskite layer lead to shunt-current leakage in devices. Herein, we report a facile method for improving the performance of perovskite solar cells by inserting a solution-processed polymer layer between the perovskite layer and the hole-transporting layer. The photovoltaic conversion efficiency of the perovskite solar cell increased to 18.1% and the stability decreased by only about 5% during 20 days of exposure in moisture ambient conditions through the incorporation of a poly(methyl methacrylate) (PMMA) polymer layer. The improved photovoltaic performance of devices with a PMMA layer is attributed to the reduction of carrier recombination loss from pinholes, boundaries, and surface states of perovskite layer. The significant gain generated by this simple procedure supports the use of this strategy in further applications of thin-film optoelectronic devices.