Reproducibility in Time and Space—The Molecular Weight Effects of Polymeric Materials in Organic Photovoltaic Devices

Abstract

The reproducibility issue is one of the major challenges for the commercialization of large‐area organic electronic devices. It involves both the device‐to‐device variation and opto‐electronic properties in different positions of a single thin film. Herein, the molecular weight effects in polymeric semiconductors with three widely used photovoltaic donor materials P3HT, PBDB‐T, and PM6 are systematically investigated. A simple but effective method is proposed to evaluate the uniformity of large‐area devices by adopting the micron‐level grid electrodes in organic thin films. An interesting phenomenon is observed that the device is gradually improved uniformly with the Mw range lower than 100 kg mol−1. In neat films, both the mobility and energetic disorder values of hole carriers exhibit relatively lower coefficient of variation (cv) in high molecular‐weight systems. After blending with the electron‐accepting materials, their bulk heterojunction films also enjoy more uniform hole transfer rates, fluorescence lifetimes, and power conversion efficiencies in single and different devices. This work not only proposes a facile approach to evaluate the electrical properties of large‐area organic thin films, but also demonstrates the relationship between molecular weight and device reproducibility in polymer solar cells. This contribution provides a new insight into the commercial large‐scale production of organic electronics.

High‐Efficiency Perovskite Quantum Dot Photovoltaic with Homogeneous Structure and Energy Landscape

“…Gaussian disorder model was used to fit their temperature-dependent electron mobility (µ e ), with the equation shown in Figure 5b, where µ 0 is the zero-field mobility, µ ∞ is the electron mobility at infinite temperature, σ is the energetic disorder parameter that indicates the width of DOS, and k is the Boltzmann constant. [52][53][54] The σ was calculated to be 61.5 and 43.3 meV for control and SPA devices, respectively, demonstrating that the SPA device has a smaller energy disorder relative to the control one. As shown in Figure 5d,e, 2D PL mapping was measured to assess the uniformity of the CsPbI 3 PQD films.…”

Desirable Uniformity and Reproducibility of Electron Transport in Single‐Component Organic Solar Cells

“…The dispersion of the carrier mobility at different sites was evaluated using the coefficient of variation ( c V ), which can be calculated using Equation () $$$$\begin{equation}{c}_v = \frac{\sigma }{{\bar{\mu }}}\ \end{equation}$$$$where σ is the standard deviation of the carrier mobility, and $$\bar{\mu }$$ is the mean carrier mobility. [ 67 ] The lower c V values indicate a lower dispersion of carrier mobilities and higher uniformity of the charge carrier transport. In Figure A,B, the PBDB‐T‐ b ‐PTY6 devices as a whole exhibit lower electron mobility with a mean mobility of 5.3 × 10 −6 cm 2 V −1 s −1 , whereas the corresponding PBDB‐T:Y6 BHJ devices show a mean mobility of 4.7 × 10 −5 cm 2 V −1 s −1 .…”

“…where 𝜎 is the standard deviation of the carrier mobility, and μ is the mean carrier mobility. [67] The lower c V values indicate…”

Organic Photovoltaic Performance Resiliency: Role of Molecular Weight in a PM7 Derivative

“…In contrast, the FF is slightly reduced to 0.62 (3% decrease), leading to a PCE of 12.4% (9% increase). Considering the large molecular weight variation of 381% (a 99 kDa difference between low and high MW), these observed device parameter changes are small as compared to reports in the literature. ,− ,− The previously discussed morphological changes likely play a significant role in determining these performances. The higher degree of intermixing in the high MW blend can be beneficial for the exciton dissociation at the donor/acceptor interface, increasing the J sc and improving the V oc .…”