On the origin of open-circuit voltage losses in flexible perovskite solar cells.

The possibility to manufacture perovskite solar cells (PSCs) at low temperatures paves the way to flexible and lightweight photovoltaic (PV) devices manufactured via high-throughput roll-to-roll processes. In order to achieve higher power conversion efficiencies, it is necessary to approach the radiative limit via suppression of non-radiative recombination losses. Herein, we performed a systematic voltage loss analysis for a typical low-temperature processed, flexible PSC in configuration using vacuum deposited C as electron transport layer (ETL) and two-step hybrid vacuum-solution deposition for CHNHPbI perovskite absorber.

Planar perovskite solar cells with long-term stability using ionic liquid additives.

Solar cells based on metal halide perovskites are one of the most promising photovoltaic technologies. Over the past few years, the long-term operational stability of such devices has been greatly improved by tuning the composition of the perovskites, optimizing the interfaces within the device structures, and using new encapsulation techniques. However, further improvements are required in order to deliver a longer-lasting technology.

Time-resolved photoluminescence on double graded Cu(In,Ga)Se - Impact of front surface recombination and its temperature dependence.

Time-resolved photoluminescence (TRPL) is applied to determine an effective lifetime of minority charge carriers in semiconductors. Such effective lifetimes include recombination channels in the bulk as well as at the surfaces and interfaces of the device. In the case of Cu(In,Ga)Se absorbers used for solar cell applications, trapping of minority carriers has also been reported to impact the effective minority carrier lifetime.

Bulk and surface recombination properties in thin film semiconductors with different surface treatments from time-resolved photoluminescence measurements.

The knowledge of minority carrier lifetime of a semiconductor is important for the assessment of its quality and design of electronic devices. Time-resolved photoluminescence (TRPL) measurements offer the possibility to extract effective lifetimes in the nanosecond range. However, it is difficult to discriminate between surface and bulk recombination and consequently the bulk properties of the semiconductor cannot be estimated reliably.

Voids and compositional inhomogeneities in Cu(In,Ga)Se thin films: evolution during growth and impact on solar cell performance.

Structural defects such as voids and compositional inhomogeneities may affect the performance of Cu(In,Ga)Se (CIGS) solar cells. We analyzed the morphology and elemental distributions in co-evaporated CIGS thin films at the different stages of the CIGS growth by energy-dispersive x-ray spectroscopy in a transmission electron microscope. Accumulation of Cu-Se phases was found at crevices and at grain boundaries after the Cu-rich intermediate stage of the CIGS deposition sequence.