Time-resolved photoluminescence studies of annealed 1.3-μm GaInNAsSb quantum wells

Investigation of the Performance of Perovskite Solar Cells with ZnO-Covered PC61BM Electron Transport Layer

Due to its high carrier mobility and electron transmission, the phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) is usually used as an electron transport layer (ETL) in perovskite solar cell (PSC) configurations. However, PC₆₁BM films suffer from poor coverage on perovskite active layers because of their low solubility and weak adhesive ability. In this work, to overcome the above-mentioned shortcomings, 30 nm thick PC₆₁BM ETLs with different concentrations were modeled. Using a 30 nm thick PC₆₁BM ETL with a concentration of 50 mg/mL, the obtained performance values of the PSCs were as follows: an open-circuit voltage (V_oc) of 0.87 V, a short-circuit current density (J_sc) of 20.44 mA/cm², a fill factor (FF) of 70.52%, and a power conversion efficiency (PCE) of 12.54%. However, undesired fine cracks present on the PC₆₁BM surface degraded the performance of the resulting PSCs. To further improve performance, multiple different thicknesses of ZnO interface layers were deposited on the PC₆₁BM ETLs to release the fine cracks using a thermal evaporator. In addition to the pavement of fine cracks, the ZnO interface layer could also function as a hole-blocking layer due to its larger highest occupied molecular orbital (HOMO) energy level. Consequently, the PCE was improved to 14.62% by inserting a 20 nm thick ZnO interface layer in the PSCs.

Carrier dynamics in (Ga,In)(Sb,Bi)/GaSb quantum wells for laser applications in the mid-infrared spectral range

We present experimental studies on low-temperature ([Formula: see text]) carrier dynamics in (Ga,In)(Sb,Bi)/GaSb quantum wells (QWs) with the nominal In content of 3.7% and the Bi ranging from 6 to 8%. The photoreflectance experiment revealed the QW bandgap evolution with [Formula: see text] % Bi, which resulted in the bandgap tunability roughly between 629 and [Formula: see text], setting up the photon emission wavelength between 1.97 and [Formula: see text]. The photoluminescence experiment showed a relatively small 3-10[Formula: see text] Stokes shift regarding the fundamental QW absorption edge, indicating the exciton localisation beneath the QW mobility edge. The localised state's distribution, being the origin of the PL, determined carrier dynamics in the QWs probed directly by the time-resolved photoluminescence and transient reflectivity. The intraband carrier relaxation time to the QW ground state, following the non-resonant excitation, occurred within 3-25[Formula: see text] and was nearly independent of the Bi content. However, the interband relaxation showed a strong time dispersion across the PL emission band and ranging nearly between 150 and [Formula: see text], indicating the carrier transfer among the localised state's distribution. Furthermore, the estimated linear dispersion variation parameter significantly decreased from [Formula: see text] to [Formula: see text] with increasing the Bi content, manifested the increasing role of the non-radiative recombination processes with Bi in the QWs.

The effect and nature of N–H complexes in the control of the dominant photoluminescence transitions in UV-hydrogenated GaInNAs

A study of certain defects in GaInNAs, and their passivation. The passivation process could lead to more efficient photovoltaic devices.