Visible light communication and LED modulation
OFDM in general is a complex baseband technology, which means it produces an I and a Q signal, which have to be mixed with a carrier wave and it's 90° shifted version, and added up before it can be used to excite a real-valued emitter (like an antenna or an LED driver).

By "I made the IFFT output real" you probably mean that you supplied the IFFT with a symmetric signal? That's nice, because it circumvents the need for a carrier frequency, but it also inherently halves your available bandwidth! Also, I can't fight the feeling that the discrete Fourier transform is not really what you're looking for if you just want to produce a real signal – the discrete cosine transform might be better suited for you.

The core question here is why you want to use OFDM in the first place.

The main motivation for OFDM comes from something that is highly inherent to the RF channel: Channels of high bandwidth aren't flat, so the equalizer for something like 20MHz of WiFi channel gets really ugly. Here, you can gain a lot by dividing your channel into orthogonal subchannels, and equalize them with a much simpler equalizer individually. I wasn't aware the same problem applies to the monochromatic VLC channel!