Multipass inkjet printing and vacuum drying of MAPbI3 perovskite for better film thickness and crystal size control.

This paper reports on the impact of outdoor temperature variations on the performance of organo metal halide perovskite solar cells (PSCs). It shows that the open-circuit voltage ( V) of a PSC decreases linearly with increasing temperature. Interestingly, in contrast to these expected trends, the current density ( J) of PSCs is found to decline strongly below 20% of the initial value upon cycling the temperatures from 10 to 60 °C and back. This decline in the current density is driven by an increasing series resistance and is caused by the fast temperature variations as it is not apparent for solar cells exposed to constant temperatures of the same range. The effect is fully reversible when the devices are kept illuminated at an open circuit for several hours. Given these observations, an explanation that ascribes the temperature variation-induced performance decline to ion accumulation at the contacts of the solar cell because of temperature variation-induced changes of the built-in field of the PSC is proposed. The effect might be a major obstacle for perovskite photovoltaics because the devices exposed to real outdoor temperature profiles over 4 h showed a performance decline of >15% when operated at a maximum power point.

We report on the performance and stability of distributed feedback lasers based on the solution-processed methylammonium lead iodide perovskite (CH3NH3PbI3). The CH3NH3PbI3 layers are processed via solution-casting in ambient atmosphere onto nanoimprinted second order Bragg gratings. This way, we achieve highly polarized surface-emitted lasing at room temperature with a linewidth of less than 0.2 nm and a laser threshold of 120 kW/cm2. The lasing is stable; no change in the laser emission within 15 h of pulsed excitation with a repetition rate of 1 kHz (corresponding to >5 × 107 pulses) is observed, exceeding the stability achieved for solution processed organic semiconductor lasers. Furthermore, adjustment of the grating period allowed the lasing wavelength to be varied over the entire bandwidth of the amplified spontaneous emission (between 781 and 794 nm). The fabrication process of nanoimprinting followed by solution-casting of the gain material demonstrates that stable CH3NH3PbI3 lasers are compatible with scalable production technologies and offers a route towards electrically pumped diode architectures.

Intermetallic Cu 11 In 9 nanoparticles with diameters of 10−30 nm were prepared via a facile, easy-to-scale-up polyol-mediated synthesis. Citrate is used as surface-capping and guarantees for efficient stabilization of the Cu 11 In 9 nanoparticles against oxidation in suspension and of powder samples in contact to air. Moreover, the citrate-capping suppresses particle-to-particle agglomeration and allows to prepare high-quality suspensions and even to redisperse Cu 11 In 9 powder samples. The latter is essential to obtain stable inks with precise element composition that can be directly used for thin-film deposition via doctor blading. Based on as-deposited thin-films, high-quality CuInSe 2 (CIS) solar cells with power-conversion efficiencies up to 7% were produced by a simple and low-cost, vacuum-free selenization process without the need of additional reducing or sintering processes. Cu 11 In 9 nanoparticles and CIS thin-films as well as the completed solar cells were characterized by various independent analytical tools, including electron microscopy (SEM/STEM), DLS, FT-IR spectroscopy, EDX, XFA, XRD, and SIMS/SNMS.