Mechanisms electroluminescence

Incorporated in a device, the LPCVD -Si H material shows electroluminescence only in reverse bias [673]. The mechanism is similar to the one described for c-Si. The PECVD a-Si H material was incorporated in a p-i-n solar cell structure, with a thickness of the intrinsic layer of 500 nm (see Section 1.11.1). Oxygen was coimplanted at 80 keV (3.2 x 10 O/em-) and at 120 keV (5.5 x lO 0/cm ), which resulted in a roughly constant oxygen concentration of 1.0% in the Er projected range in the middle of the intrinsic a-Si H layer. Electroluminescence is observed under forward bias [674]. 

In thin films of electroluminescent conjugated polymers, Kanner et al. [12] and Yan et al. [13] explained the quenching of PL by invoking an exciton migration mechanism to nonradiative traps based on the Balagurov-Vaks model [14], The survival probability of an exciton on a 1-D lattice (fi- = 1/3) is characterized by a diffusion time t(i. For times t t,i. the PL intensity follows... 

The process shown in Fig. 90(b) is favoured by the known position of the band edges in alkali, the similarity with the electroluminescence induced by persulphate, and the energy of the [Fe(CN)6]3, 4 redox couple. Either mechanism would, however, be consistent with the observation that the onset of electroluminescence coincides, approximately, with the flat-band potential, as shown in Fig. 91. Interestingly, the photoluminescence reaches a maximum at more negative potentials, a result not predicted by either model, as shown in Fig. 91 [167],... 

A thin film ( 100 nm) of a PPV derivative is sandwiched between two electrodes supported on a solid substrate, such as glass, a flexible plastic substrate, such as poly(propylene), or even a thin film of aluminium, see Figure 6.1. The device substrate provides the mechanical support to the anode, electroluminescent polymer layer and the cathode. The anode is transparent in... 

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