I actually wrote:
Noise which is related to smoothness and DR depends mostly on the number of photons captured.
So you quote me selectively. There are several factors affecting noise. The major source of noise is shot noise that is coming from the statistical distribution of incident photons. Quantum efficiency does have little to do with noise. If QE is low you can increase exposure to compensate. ETTR, expose to the right.
How many photons a pixel can hold depends mostly on it size. But how many photons a sensor can detect depends on the silicon area. So larger sensors have an advantage, other factors being constant.
DR is a technical term and is essentially FWC (Full Well Capacity) / read noise with both expressed in electrons. Roughly one electron corresponds to one photon.
The Fuji super CCD has some trick using dual sensors. I imagine that for that to work the highlight sensels must have some kind of grey filter or aperture. Anyway the super CCD is not a mainstream technology now.
The reason that the D7000 has an excellent DR is that it has very little readout noise. That depends on the sensor having a massive array of on chip ADC (Analog to Digital Converters).
If you check DxO-mark you can see that the Nikon D7000 has similar DR to the Phase One IQ180 (albeit at much higher ISO) but the IQ-180 has better tonal range. Tonal range is similar to DR but does not use SNR=1 criteria but a stiffer one.
My guess is that the D7000 sensor has a readout noise of perhaps 2 electrons and the IQ-180 about 12 electrons.
DR depends on many factors.
Sensor size actually does not have that much do do with it.
Sensor efficiency and quality has a lot more to do with it.
How much space there is between photosites... but even that is not always true.
Fuji's super CCD had better dynamic range than anything else for many years and it had large spaces between
photosites, but had a dual array. Photosites for highlights and photosites for shadows and midtones.
Just look at the excellent dynamic range of the D7000 with it's tiny sensor.
D7000 has the same dynamic range as the Phase One IQ180
D800 has better dynamic range than the IQ180, but a sensor half the area size.