Читать книгу Organic Electronics for Electrochromic Materials and Devices - Hong Meng - Страница 17

The optical or EC memory (also called open‐circuit memory) of an EC material can be defined as the propensity of the material to retain its redox/colored state upon removing the external bias. Usually, the memory effect are often observed in film‐state EC materials such as conjugated polymers, which well adhered onto the electrode, and hence restrict the movement of the electrons. In contrast, some solution‐based ECDs (e.g. viologens) will exhibit a self‐erasing effect, which means the colored state disappeared rapidly in the absence of applied voltage because the electrons diffuse freely in this type of device. The memory effect is useful for the energy‐saving devices and also can be applied for data storage. Figure 1.9 shows an optical memory test. The short‐term memory was investigated by applying a potential pulse for 2 seconds prior to forming the open‐circuit state for 100 seconds; the transmittance change at 423 nm was monitored simultaneously (Figure 1.9a). Then a long‐term memory is also studied by applying a potential for two seconds and removing the bias for one hour (Figure 1.9b). The EC conjugated polymers remain in the initial transmittance contrast well in the absence of an applied voltage, which exhibits a good optical memory.

Figure 1.9 Open‐circuit memory tests of PBOTT‐BTD spray coated on an ITO‐coated glass slide in 0.1 M TBAPF6/ACN at 423 nm: (a) short‐ and (b) long‐term performance.

Source: Li et al. [21].