The exciton dynamics of violanthrone-79 are investigated in solution and in the solid state. In solution, the photoprepared singlet is found to exhibit a strong ground-state bleach and stimulated emission feature, but when sensitized in its triplet state, it exhibits only a narrow and weak ground-state bleach. As supported by density functional theory calculations, this is explained by the triplet state having absorptions in the same region, with a similar oscillator strength, as the ground-state molecule. In solid films, the excited singlet is found to survive for up to 200 ps, giving way to a long-lived transient absorption spectrum with characteristics reminiscent of the triplet in solution. This is interpreted in terms of singlet fission in the solid film.

This paper reports on the execution and results of an interdisciplinary design project using advanced luminescent solar concentrator PV (LSC PV) technologies in new contexts of use such as the built environment, mobility and consumer products. In the past years LSC PV technologies have been rapidly maturing showing increasing efficiencies up to 10% with high expectations regarding further improvements at low costs. In this context in 2019 a summer school of one week took place aiming at optimally combining design features of LSC PV devices and further enhancements of their performance by scientific research. This design-driven project resulted in several interesting new LSC PV applications which are presented in this paper.

Back‐contact architectures offer a promising route to improve the record efficiencies of perovskite solar cells (PSCs) by eliminating parasitic light absorption. However, the performance of back‐contact PSCs is limited by inadequate carrier diffusion in perovskite. Here, we report that perovskite films with a preferred out‐of‐plane orientation show improved carrier dynamic properties. With the addition of guanidine thiocyanate, the films exhibit carrier lifetimes and mobilities increased by 3–5 times, leading to diffusion lengths exceeding 7 μm. The enhanced carrier diffusion results from substantial suppression of nonradiative recombination and improves charge collection. Devices using such films achieve reproducible efficiencies reaching 11.2 %, among the best performances for back‐contact PSCs. Our findings demonstrate the impact of carrier dynamics on back‐contact PSCs and provide the basis for a new route to high‐performance back‐contact perovskite optoelectronic devices at low cost.

<div>The exciton dynamics of violanthrone-79 are investigated in solution and in the solid</div><div>state. In solution, the photo-prepared singlet is found to exhibit a strong ground-state bleach</div><div>and stimulated emission feature, but when sensitized in its triplet state, exhibits only a narrow</div><div>and weak ground-state bleach. As supported by density functional theory calculations,</div><div>this is explained by the triplet state having absorptions in the same region, with a similar</div><div>oscillator strength, as the ground state molecule. In solid films, the excited singlet is</div><div>found to survive only 100 ps, giving way to a long-lived transient absorption spectrum with</div><div>characteristics reminiscent of the triplet in solution. This is interpreted in terms of singlet</div><div>fission in the solid film.</div>