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In the past five years, perovskite solar cells (PSCs) based on organometal halide perovskite have exhibited extraordinary photovoltaic (PV) performance. However, the PV measurements of PSCs have been widely recognized to depend on voltage scanning condition (hysteretic current density-voltage [J-V] behavior), as well as on voltage treatment history. In this study, we find that varied PSC responses are attributable to two causes. First, capacitive effect associated with electrode polarization provides a slow transient non-steady-state photocurrent that modifies the J-V response. Second, modification of interfacial barriers induced by ion migration can modulate charge-collection efficiency so that it causes a pseudo-steady-state photocurrent, which changes according to previous voltage conditioning. Both phenomena are strongly influenced by ions accumulating at outer interfaces, but their electrical and PV effects are different. The time scale for decay of capacitive current is on the order of seconds, whereas the slow redistribution of mobile ions requires several minutes.

An overview of the state of the art dye solar module technology and innovations required for further development is presented.

Despite spectacular advances in conversion efficiency of perovskite solar cell many aspects of its operating modes are still poorly understood. Capacitance constitutes a key parameter to explore which mechanisms control particular functioning and undesired effects as current hysteresis. Analyzing capacitive responses allows addressing not only the nature of charge distribution in the device but also the kinetics of the charging processes and how they alter the solar cell current. Two main polarization processes are identified. Dielectric properties of the microscopic dipolar units through the orthorhombic-to-tetragonal phase transition account for the measured intermediate frequency capacitance. Electrode polarization caused by interfacial effects, presumably related to kinetically slow ions piled up in the vicinity of the outer interfaces, consistently explain the reported excess capacitance values at low frequencies. In addition, current-voltage curves and capacitive responses of perovskite-based solar cells are connected. The observed hysteretic effect in the dark current originates from the slow capacitive mechanisms.

Anion/cation vacancies located at different interfaces in perovskite solar cells may modify the electronic energy landscape, hampering charge extraction, and presumably contributing to the observed J–V hysteresis.

In this work we present a solar cell structure where the concept of intermediate band is exploited by, a high energy barrier AIGaAs material with embedded InAs-based quantum dots via a multistep growth approach. In this way the intrinsic issues related to different surface kinetics of involved species (Ga, In and Al adatorns) and affecting crystal quality are successfully overcome. With respect to energy band engineering of the cell, this growth approach introduces a two-dimensional quaternary layer and consequently an additional energy band, between the host junction and the dot energy levels. This band results strongly related to the quantum dot states by thermal transferring and inter-level filling processes. Moreover, low temperature (up to 100 K) photocurrent generation via additional infrared absorption is promoted by the employed band engineering, thus representing an effective method to extend intermediate band solar cell design flexibility.